There conventionally is a power transmission device provided with a one-way clutch. For example, Patent Literature 1 discloses a hybrid vehicle including an internal-combustion engine, an electric device to which rotation from the internal-combustion engine is input, an electric motor driven by a supplied current, a differential gear device including at least three gear elements, a first gear element coupled to the electric device, a second gear element coupled to an output shaft, and a third gear element coupled to the internal-combustion engine, and braking means which stops rotation of the third gear element.